This project is concerned with the basic genetics of the ciliated protozoan, Tetrahymena pyriformis. Of particular concern are 1) the formal genetics of the biological species designated as "syngen 1", with particular attention to developing adequate linkage groups for the five pairs of chromosomes, 2) the regulatory systems responsible for the timing of "allelic exclusion", and the relationship between these systems and the structure of the chromosomes and the macronucleus, 3) the roles of genes and of preexisting structures in cellular morphogenesis, and 4) evolutionary and molecular distances among the genetic species (syngens). These studies involve electrophoresis, immunological techniques, mutagenesis, and cytochemistry in addition to breeding analysis.